1. Field of the Invention
The present invention is directed to updating speech recognition grammars and, more particularly, to automatically updating speech recognition grammars, so that users can receive responses to general questions, such as questions related to current events and locations.
2. Description of the Related Art
Currently, speaker independent speech recognition systems use a limited vocabulary to increase recognition accuracy. Phrases that can be recognized are part of a “grammar.” The grammar specifies every possible combination of words which may be spoken by the user. Some of the many commercially available speech recognition systems include Speechworks from Speechworks International, Inc. of Boston, Mass.; Nuance from Nuance of Menlo Park, Calif. and Philips Speech Processing available from Royal Philips Electronics N.V. in Vienna, Austria. All of these systems and many others utilize grammars that can be modified for specific applications. By limiting the size of the grammar, speech recognition systems are now able to recognize spoken commands from many users without requiring training of the system to the way each user pronounces words. Such speaker independent systems can be contrasted with speech recognition systems used with word processing programs that have large vocabularies, must ideally adapt to each user's pronunciation, and have internal grammatical representations, such as statistical language models.
In some applications, the grammars are modified for individual users to recognize terms that the user has indicated might be spoken, such as names of stocks in the user's portfolio. The grammar may even be modified during interaction with the user to include only those words that can be spoken at the current position within a command interface. For example, a voice activated telephone might have an initial grammar limited to “call”, numbers, and names that have been recorded by the user for speed dialing, like “home”, “mom”, etc. After receiving a command to call a number input by speaking the digits of the number, the phone may request confirmation with words in the grammar limited to “yes”, “no” and “hang up”. An initial grammar is loaded when the application begins, for example, before a call is received by telephone. This grammar defines the basic functionality of the system. It may include subgrammars, which can be activated or deactivated depending on the state of the application. For example, when the application asks a yes/no question, it may activate a subgrammar containing only the words yes and no. Similarly, when the application requests a phone number from the user, it may activate a grammar consisting of only seven or ten digit number strings.
Other portions of the grammar may be specific to a particular user of the system, and will be loaded once that user has been identified. This might include an address book of phone numbers, or stock symbols in a personal portfolio. An example of an address book grammar might be the phrase “Call John Jones,” which can be associated with a phone number for John Jones from a specific user's address book. The grammar would not include this phrase for any user who did not have John Jones in his or her address book.